Transport belt drive control device, image forming device, and transport belt drive control method

Abstract

In a transport belt drive control device, a first detection unit has a first resolution and indirectly detects a feed amount of a transport belt, a control unit controls drive of the transport belt based on an output of the first detection unit, and a second detection unit has a second, lower resolution and directly detects the feed amount of the transport belt. The control unit is configured to switch, when an output of the second detection unit is determined as not allowing detection of a stop position of the transport belt, the direct detection of the belt feed amount by the second detection unit to the indirect detection of the belt feed amount by the first detection unit, so that the drive of the transport belt is controlled based on the output of the first detection unit.

1. A transport belt drive control device comprising:
 a first detection unit having a first resolution and indirectly detecting a feed amount of a transport belt; 
 a control unit controlling drive of the transport belt based on an output of the first detection unit; and 
 a second detection unit having a second resolution lower than the first resolution and directly detecting the feed amount of the transport belt, 
 wherein the control unit is configured to switch, when it is determined that an output of the second detection unit having the second resolution does not allow detection of a stop position of the transport belt, the direct detection of the transport belt feed amount by the second detection unit to the indirect detection of the transport belt feed amount by the first detection unit, so that the drive of the transport belt is controlled based on the output of the first detection unit. 
 
   
   
     2. The transport belt drive control device of  claim 1  wherein the first detection unit comprises:
 a rotary scale disposed with a given interval on a circumference of a disc attached to a revolving shaft driving the transport belt; 
 an indirect encoder generating an output signal whenever the rotary scale is detected; and 
 an indirect counter counting the output signal of the indirect encoder. 
 
   
   
     3. The transport belt drive control device of  claim 1  wherein the second detection unit comprises:
 a belt scale disposed with a given interval on a circumference of the transport belt; 
 a direct encoder generating an output signal whenever the belt scale is detected; and 
 a direct counter counting the output signal of the direct encoder. 
 
   
   
     4. The transport belt drive control device of  claim 1  wherein the control unit comprises:
 a computation unit computing a reference stop value based on a given stop position of the transport belt, the reference stop value indicating a movement amount of the transport belt for the given stop position and being expressed as a corresponding count value of the indirect encoder; 
 a subtraction unit subtracting from the reference stop value a count value of the indirect counter equivalent to a single count of the direct counter every time a count value of the direct counter is incremented; and 
 a stopping unit stopping the transport belt when a result of the subtraction from the reference stop value is below the count value of the indirect counter equivalent to the single count of the direct counter and a resulting count value of the indirect counter is equal to the result of the subtraction from the reference stop value. 
 
   
   
     5. The transport belt drive control device of  claim 4  wherein the stopping unit is configured to decrement a result of the subtraction from the reference stop value whenever a count value of the indirect counter is incremented, and to stop the transport belt when the result of the subtraction from the reference stop value is equal to zero. 
   
   
     6. The transport belt drive control device of  claim 1  wherein the first detection unit comprises an indirect counter counting an output signal generated by an indirect encoder whenever a rotary scale is detected, the second detection unit comprises a direct counter counting an output signal generated by a direct encoder whenever a belt scale is detected, and the control unit comprises a reset unit resetting a count value of the indirect counter whenever a count value of the direct counter is incremented. 
   
   
     7. The transport belt drive control device of  claim 1  wherein the first detection unit comprises an indirect counter counting an output signal generated by an indirect encoder whenever a rotary scale is detected, the second detection unit comprises a direct counter counting an output signal generated by a direct encoder whenever a belt scale is detected, and the control unit is configured to subtract a count value of the indirect counter equivalent to a single count of the direct counter from the reference stop value after a feed amount control of the transport belt is started and before a count value of the direct counter is changed. 
   
   
     8. An image forming device in which an image recording unit forms an image on a recording medium transported by a transport belt, and a transport belt drive control device controls drive of the transport belt, the transport belt drive control device comprising:
 a first detection unit having a first resolution and indirectly detecting a feed amount of a transport belt; 
 a control unit controlling the drive of the transport belt based on an output of the first detection unit; and 
 a second detection unit having a second resolution lower than the first resolution and directly detecting the feed amount of the transport belt, 
 wherein the control unit is configured to switch, when it is determined that an output of the second detection unit having the second resolution does not allow detection of a stop position of the transport belt, the direct detection of the transport belt feed amount by the second detection unit to the indirect detection of the transport belt feed amount by the first detection unit, so that the drive of the transport belt is controlled based on the output of the first detection unit. 
 
   
   
     9. A transport belt drive control method comprising steps of:
 providing a first detection unit having a first resolution and indirectly detecting a feed amount of a transport belt; 
 controlling drive of the transport belt based on an output of the first detection unit; and 
 providing a second detection unit having a second resolution lower than the first resolution and directly detecting the feed amount of the transport belt, 
 wherein the controlling step is configured to switch, when it is determined that an output of the second detection unit having the second resolution does not allow detection of a stop position of the transport belt, the direct detection of the transport belt feed amount by the second detection unit to the indirect detection of the transport belt feed amount by the first detection unit, so that the drive of the transport belt is controlled based on the output of the first detection unit. 
 
   
   
     10. The transport belt drive control method of  claim 9  wherein the first detection unit comprises an indirect counter counting an output signal generated by an indirect encoder whenever a rotary scale is detected, and the second detection unit comprises a direct counter counting an output signal generated by a direct encoder whenever a belt scale is detected, and wherein the controlling step comprises:
 computing a reference stop value based on a given stop position of the transport belt, the reference stop value indicating a movement amount of the transport belt for the given stop position and being expressed as a corresponding count value of the indirect encoder; 
 subtracting from the reference stop value a count value of the indirect counter equivalent to a single count of the direct counter every time a count value of the direct counter is incremented; and 
 stopping the transport belt when a result of the subtraction from the reference stop value is below the count value of the indirect counter equivalent to the single count of the direct counter and a resulting count value of the indirect counter is equal to the result of the subtraction from the reference stop value.